The presence of transparent elements in vehicle roofs has given rise to the design of sunblinds adapted to the configuration of the area to be covered.
This type of device depends largely on the area and its configuration both in terms of form and aspect of the perimeter edge and its curvature. The availability of a technical solution with a given configuration does not guarantee the viability of an application to a greater area or one with different curvature as a simple scaling for example, can give rise to components with inertias which exceed the admissible values for the means of retention or guiding.
Modifying the guiding means is not always possible by scaling since its location in the vehicle roof imposes severe spatial restrictions because, for example, the height of the device reduces habitability in the interior of the vehicle.
As a result, changing the dimensions of the transparent element to be covered in the majority of cases requires a change in the solutions applied to each of the parts of the shading device.
Returning to the blocking means, the use of increasingly large transparent elements gives rise to sunblinds which, due to their greater dimensions, also show greater inertial effects.
These inertial effects are important both in the braking and acceleration of the vehicle since the sunblind is impelled and is displaced longitudinally according to the vehicle's direction. This undue displacement does not occur if the blocking means are able to provide sufficient retention.
Sufficient retention is achieved with brake shoes which apply the necessary pressure to ensure that the frictional or interlocking forces used are able to balance the inertial forces.
This pressure force is usually carried out by springs which can be used as chocks. The release of these springs is achieved by applying greater force from the handle device. When this force is high, the manual action of the sunblind becomes difficult or even impossible for users with little strength.
The patents with publication numbers EP1201473 and EP1353037 make use of cables or traction bars which act directly on the pressure spring of the retention brake shoes. The release of the blocking means is achieved by direct traction from the handle device. It is possible that the handle device is provided with some means of increasing the tension either because it causes a control to rotate with a different curvature radius in the cable winding from that at the point of application of the force, or either another medium situated in the central point of the handle device.
The drawings in the patent with publication number DE10338722 shows a support point which is almost precisely between the brake shoe and the sunblind guide.
The drawings show that this brake shoe is withdrawn by means of a cable with a cover which enables the brake shoe to be retracted directly overcoming the resistance offered by the pressure spring against the guide.
In all the cases known the brake shoe support is exercised on the elastomeric material with a retention based on a retention force which principally verifies being proportional to the friction coefficient and the applied force; or it either establishes the retention by incorporation of teeth which improve the braking force.
The present invention proposes the use of an elastomeric component with properties in respect of distortion which give rise to a different form of retention as well as the incorporation of means for multiplying force situated in the point of application of the blocking combined with a handle device with symmetrical conduct in order to make the unblocking of the sunblind more effective, thus facilitating operation.